The reliability of the obtained \(H_{c2}\) (0) value is guaranteed by the direct electrical transport measurements at enough high magnetic fields and at low temperatures. As a key indicator in the applications of superconducting materials, the \(H_{c2}\) (0) of K\(_3\) C\(_{60}\)  is little bit higher than that of Nb\(_3\) Sn with lower \(T_c\)  of 18 K [1]}, a typical three-dimensional superconductor well known as superconducting magnets. Interestingly, our \(H_{c2}\) (0) value for K\(_3\) C\(_{60}\)  at ambient pressure is even comparable to those of \(fcc\)  CeH\(_{10}\)  with much higher \(T_c\) =115 K at pressure of 95 GPa [2]} and ThH\(_{9}\)  with \(T_c\) =151 K at 170 GPa [3]}. However, the need of high pressures to access the superconducting state in these superhydrides limits their technological applications. The larger \(H_{c2}\) (0) for K\(_3\) C\(_{60}\)  with the higher \(T_c\)  compared to those in Nb\(_3\) Sn offers the attractive opportunities for the technological applications due to the rich carbon abundance on the Earth as well as the low cost. Therefore, the present experimental finding opens a window for future developments and designs of the three-dimensional superconducting magnets based on this material.
